Abstract : A modular environmental assessment method of road sections based on Life Cycle Analysis and developed by LCPC, has been extended to impacts calculations and alternative materials assessment. The purpose of this thesis was to compare highway design using natural and alternative materials and to extend the associated tool to urban areas. Besides a detailed analysis of the practice tool clarity by non specialists of the environmental framework was carried out. The urban design has been implemented on the basis of classical design. The extension to alternative materials has been done for blast furnace slag. Several applications for pavement typical cases as weil as for engineering works studies are presented. Besides, an investigation by means of interviews and questionnaires was conducted among various stakeholders, to identify the weight of environmental criteria in the decisionmaking process.